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How to increase the injection rate of plastic molding machines?

2025/06/23 By Topstar

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When pursuing the goal of increasing the output of plastic molding machines during injection molding, one key factor that needs improvement is the injection rate. The injection rate is the speed at which the molten resin is pressed into the mold, and it is also one of the key factors that determine the cycle time and total output of any injection molding machine. Faster injection rates result in shorter cycle times, enabling the production of more parts per hour. Therefore, we need to improve the injection rate of plastic molding machines by adjusting various factors, including the geometry of the screw and barrel, the nozzle design, and the process parameters.

Optimizing the screw, barrel and nozzle design of plastic molding machines

The mechanical design of plastic molding machines forms the basis for accelerating injection molding. The compression ratio of the screw of Topstar’s high-speed plastic molding machine is between 1:1.2 and 1:1.4, which can accelerate the melting of the feed zone, thereby supplying more homogeneous resin to the nozzle. At the same time, we will increase the inner diameter of the barrel by 5-10 mm and match it with a deeper metering thread to reduce the melt pressure during high-speed injection molding. For example, in production trials for automotive interiors, upgrading the standard 45 mm screw to a 50 mm screw increased melt throughput by more than 20%.

Nozzle design is equally important. Our TE series electric injection molding machines are equipped with interchangeable nozzles featuring optimized nozzle tip geometry, such as streamlined, tapered flow nozzles, which minimize flow resistance and ensure polished inner surfaces to prevent early freezing during rapid filling, thereby maintaining high injection capacity.

Optimizing the screw, barrel and nozzle design of plastic molding machines

Using electric servo systems

Traditional hydraulic systems may be robust, but they sometimes lack the precise, instantaneous response required for peak injection rates. Therefore, in modern injection molding production, to improve injection efficiency, electric plastic molding machines are selected, utilizing highly responsive all-electric drive systems to provide high-speed plunger acceleration and deceleration. This directly translates into breakneck injection speeds while maintaining precise control of the pressure curve. The instantaneous response of these systems eliminates lag, ensuring that the molten plastic enters the mold cavity at the maximum speed that the material and part geometry can achieve, thereby significantly improving the overall injection rate.

Secondly, our TE Series all-electric plastic molding machines feature direct-drive ball screws and high-torque servo motors for faster acceleration and deceleration. These machines can achieve injection speeds up to 400 mm/s, nearly twice that of a standard hydraulic press, while also providing repeatable accuracy.

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Adjusting the process parameters of the plastic molding machines

Adjusting the process parameters during production Increases the injection rate of the plastic molding machine. First, increase the melt temperature to reduce viscosity within the range recommended by the resin supplier. Next, increase the injection speed in controlled increments and monitor the cavity pressure profile to detect signs of jetting or burning. Then, adjust the back pressure down to 5-8 bar to minimize screw slippage while preventing unmelted resin.

Operators typically employ a multi-stage speed profile, then gradually decelerate near the gate freeze point. This approach, implemented through the control touchscreen of the injection molding machine, can reduce fill time by up to 30% while maintaining dimensional accuracy, ensuring that your plastic injection molding machine operates at peak speed without compromising quality.

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Achieve Precise Melt Temperature Control

Precise temperature management also enables higher injection speeds on plastic molding machines. Specifically, if the melt temperature is too low, viscosity increases dramatically, forcing the injection molding machine to push the material into the mold at a higher speed and slower rate. Conversely, overheating can cause polymer degradation. Topstar uses a highly responsive, multi-zone barrel heating and temperature control system. This ensures that the polymer always reaches its ideal processing temperature. This process keeps the melt at a lower, more stable viscosity and significantly cuts flow resistance during high-speed injection. Additionally, we recommend using valve-controlled hot runner nozzles in critical applications to prevent frozen material blocks that can hinder injection recovery. In our field tests, using a high-flow manifold reduced the filling time of a 32-cavity cover mold by 0.2 seconds, equivalent to producing 200 more parts per hour.

Leverage real-time monitoring and control technology.

To maintain a high injection rate, you need adaptive, data-driven control. Topstar’s equipment features a real-time process monitoring system that tracks injection speed, cavity pressure, and screw position in milliseconds. Therefore, by implementing pressure control at the mold gate, the system automatically adjusts the speed to maintain the target pressure profile, ensuring consistent cavity filling over thousands of cycles. At the same time, automatic deceleration is employed at the end of filling to prevent burrs, as well as customizable curve storage, which allows operators to select the optimal injection curve for each mold and maintain optimal injection performance.

Achieving high injection rates

Increasing the injection rate of plastic molding machines requires optimizing screw, barrel and nozzle design, adjusting process parameters, adopting electric drive systems, and deploying real-time monitoring technology to increase injection rates, thereby reducing cycle time, increasing output by 20%, and maintaining stable part quality. From precision mechanical design to high-torque electric servo drives and adaptive data-driven monitoring, each element works together to maintain optimal performance without compromising part quality.

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